Late snowfall in the American West is part of pattern
By mid-century, the Pacific states could lose much of their snowpack
|DENVER
EVERY DECEMBER residents of Denver, Colorado hang holiday lights and decorate trees—and the occasional cactus—in their front yards. But this year one thing is missing from the festive picture: snow. As of December 8th, Denverites had yet to see any snow land on their yellowing lawns, making it the latest first snowfall since records began in 1882. And Colorado’s capital is not alone, for the white stuff is scarce this year across the American West. A new study suggests future winters might not bring much either.
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The snow that builds up in mountain ranges over the winter, called snowpack, is a natural reservoir. In the spring, when it melts, its waters replenish rivers, man-made reservoirs and soil. The amount of water that makes it into reservoirs each year depends on temperatures, evaporation and run-off, or how much soaks into the ground. But warmer winters in the western states, one consequence of climate change, have led to a decline in average snowpack. One study published in 2018 found that annual snowpack in the region had decreased by 15-30% since 1915.
The future looks bleaker still. A new paper by researchers at the Lawrence Berkeley National Laboratory in California found that mountain snowpack in the West could decline by an average of 25% by 2050. The rate varies across four mountain ranges studied. The Sierras and the Cascades could see a 45% decline in snowpack by mid-century, compared with 20-30% declines for the Rockies and the Wasatch/Uinta. So a snowless future seems more imminent in California and the Pacific Northwest than further inland.
The West has had bouts of “snow drought” before. But they look set to become more common. Researchers suggest that California could experience persistent “low-to-no snow” by the 2050s with the Rocky Mountain states following in the 2070s. Many places are already preparing for a drier future. California’s Department of Water Resources recently warned that next year the State Water Project, a storage and delivery system that runs through the middle of the state, will initially only provide water for “health and safety” needs. Arizona is readying for cuts to its allotment of the Colorado River, which supplies water to 40m people across the south-west. ■
